Nucleation, stabilization, annihilation, and transformation of topological spin textures for reservoir computing

Topological spin textures have been considered as one of the prominent candidates for low power consumption physical reservoir computing. In this work, we fabricated a micro-sized symmetry breaking multilayered disk composing of stacks FeCo/CoNi/Pt as a reservoir for topology spin textures. We found the nucleation, stabilization, annihilation of topological spin textures in the disk can be controlled by a current in a ring outside the disk. We also found the transformation between skyrmions and bimerons can be achieved by simply tailoring the amplitude and frequency of the AC current. The phenomenal can be explained by the concurrent effects of oersted field, joule heating, and magnetostriction of the current. Due the concurrent effects, we find an abnormal dependance of magnetization on the applied current at low current frequency. Namely, the films keep perpendicular magnetization at low applied currents but transition to in-plane magnetization with sufficiently large current. Photo-elastic microscope observations show a sufficient large stress is created if we apply a current to the ring coil. Nucleation, stabilization, annihilation, and transformation of the topological spin textures provided a robust, nonlinearity, and memory physics system for carrying out reservoir computing.